Patent GB-1383933-A (GB)
Title: Vehicle safety apparatus
IPC: G01S13/931
Filed: 1972-05-12
Abstract: 1383933 Pulse radar SPERRY RAND CORP 12 May 1972 [20 May 1971] 22355/72 Heading H4D A vehicle safety system includes a transmitter producing two successive signals; a receiver and two circuits for producing first and second signals corresponding to reflections of the successive transmitted signals; a sensor for indicating vehicle speed above a predetermined value arid a safety device responsive to the simultaneous presence of the first and second signals with a sensor output. In an automobile collision protection system, Fig. 1, sub-nanosecond pulses are radiated from a parallel wire transmission line antenna 5 mounted behind a dielectric radiator grille on vehicle 1. Reflections from vehicle 2 are received by a similar antenna 6 and passed via a dispersionless transmission lines (using TEM mode or propagation) to near- and far-gated detectors 31a, 31. Far gated detector 31 is sensitive to reflections in a range of from two to eight feet and produces a 119 ms. pulse in response thereto. (Detector 31 is inhibited after reception of the first echo.) Near gated detector 31a responds to echoes from a range of from two to three feet and produces a ms. pulse. A speed sensor 40 produces an output if the vehicle velocity is above a preset value. Coincidence of outputs from both detectors and the speed sensor at gate 35 actuates safety devices such as an inflatable gas bag restraint, vehicle brakes. A warning light and horn may also be actuated. Gated detectors, Fig. 8.-Synchronizing pulses from generator 11 (Fig. 1), turn on avalanche transistor 104. The voltage pulse at the collector travels along delay line L, is reflected from the open circuit end and returns to turn off the transistor 104. Thus a pulse is produced at the emitter whose length is determined by delay 63. High level transients at the leading and trailing edges of this pulse are removed by low pass filter 67. The positive pulse from filter 67 is inverted by transistor 119 whose bias is set by potentiometer 125 to ensure that normally a sufficient current is passed through transistor 119 to block transistor 74. When the positive pulse arrives transistor 119 is turned off unblocking transistor 74 which is biased by FET 143 providing a constant current. While transistor 74 is unblocked, echo signals which arrive via transmission line 30a are passed to the output transmission line 48a. To provide the inhibition of the far gated detector a large capacitor is connected to the output and also connected to ground through a resistor. Any echo pulse passed to the output discharges the capacitor thus blocking further echoes until it is recharged. Alternatively, the detector output is passed to a pulse stretcher whose output drives a conventional inhibitor (Fig. 9, not shown).  Velocity sensor, Fig. 13.-The velocity sensor 40 (Fig. 1), is provided by a cam 265 mounted on the drive shaft 262 of the pointer 261 in the automobile speedometer. At low velocities cam 265 prevents light from source 266 reaching detector 267. At a high enough velocity the cam is rotated out of the light beam and a signal is passed via leads 35c to the AND gate 35 of Fig. 1. The disabling of gate 35 at low speeds enables the vehicle to be parked behind another vehicle without operating the inflatable gas bag.